In wireless communications systems of the art, a variety of transmission protocols have been developed for providing wireless service to users. Exemplary network services based on such transmission protocols include High Rate Packet Data (HRPD), Long Term Evolution (LTE) and Universal Mobile Telecommunications System (UMTS). Each of these network services is defined in terms of a particular Radio Access Technology (RAT), and, in general, the RAT defining each different transmission protocol requires a unique RF configuration for transmission and reception of communications based on a given RAT.
Heterogeneous networks (HetNets) are now being developed wherein cells of smaller size are embedded within the coverage area of larger macro cells, primarily to provide increased capacity in targeted areas of data traffic concentration. Such heterogeneous networks try to exploit the spatial variations in user (and traffic) distribution to efficiently increase the overall capacity of the wireless network.
Based on the cell size, Heterogeneous networks are generally classified according to two major types: Large cells, which include macro cells and macro relays; and Small cells, which include micro cells, pico cells, Home evolved node B (HeNB)/femto cells (usually privately maintained) and small relays. It is a common deployment scenario that macro coverage is overlaid with spotty small cell coverage. A mobile station, or User Equipment (UE), communicating with a macro cell base station will normally do so at a higher transmission power level than for a link from the mobile/UE to a (usually nearby) overlaid small cell and this transmission power difference often creates significant interference management problems in the HetNet.
Additionally, due to a limited spectrum resource, system operators may require sharing of the same carrier by the macro cells and the small cells of the HetNet. In that circumstance, a problem may occur when coverage is overlapped between a macro and one or more small cells. In such coverage overlap, UEs connected with a small cell may experience excessive interference in its reverse link from a nearby UE that is communicating with the macro cell—such UE to macro-cell transmission typically occurring at much higher transmission power levels than for UE to small-cell transmission.
While techniques are generally known for Inter-Cell Interference Coordination (ICIC) among neighboring macro cells, it is difficult to conduct per-UE network controlled ICIC between the macro cell and small cells in a heterogeneous network. Although a few techniques have evolved for addressing such intra-HetNet interference issues—e.g., resource splitting between macro and small cells, such techniques require tight synchronization and complicated scheduling on a per UE basis and generally result in reduced overall spectral efficiency for the network.